Automatic throttle control



April 5, 1960 R. R. STRATTON AUTOMATIC THROTTLE CONTROL Filed April 25,1957 sgli INVENTOR.

Paw/1w A. 5754770 BY flM, M

AT TOPNE Y5:

AUTOMATIC THROTTLE CONTROL Ronald R. Stratton, Cleveland, Ohio,

Equipment Company, of Ohio assignor to Stratton Cleveland, Ohio, acorporation This invention relates to an automatic speed control forinternal combustion engines and more particularly to an automaticthrottle control for the engines of motor trucks embodying hydraulicallyoperated devices such as dump bodies, lift platforms and the like inwhich the hydraulic pressure for operation of the device is furnished bya pump driven by a power take off from the truck engine.

Large numbers of trucks having hydraulic devices operated by power takeoff means driven by the engine are in use at the present time. Suchtrucks customarily embody a hydraulic motor, usually in the form of acylinder, arranged to actuate a dump body, lift platform and the like orto perform some other desired function; a valve for controlling the flowof fluid to the hydraulic cylinder, the valve ordinarily being disposedoutside of the cab of the truck at a point where the operator canobserve the motion of the body, platform or the like; a pump forsupplying hydraulic fluid under pressure to the cylinder; appropriatefluid connections for the devices; and a power take off usuallyembodying auxiliary gearing so that the main truck engine can beemployed to drive the pump,

The ordinary idling speed of the engine is not suflicient to furnishsufiicient fluid under pressure to operate the hydraulic cylinder at areasonably rapid rate of speed. Accordingly, operators of such trucksfrequently pull out the hand throttle in the cab of the trucksufliciently to race the engine under no load at the speed which theoperator thinks is proper. Then the operator leaves the cab, goes to hisstation adjacent the hydraulic control valve and by suitablemanipulation of the valve, controls the operation of the cylinder. Theresult is that the truck engine is raced at excessive speeds forconsiderable periods of time, fuel consumption of the engine isexcessive and the engine is subject to injury and rapid wear because ofracing under no load. Another mode of operation employed by some driversis to move the control valve to operating position with the en ineidling, then to go back to the cab and manipulate the throttle whileleaning out of the door of the cab in an effort to observe the positionof the body, platform or the like. This mode of operation is dangerousbecause it requires the operator to be away from his proper position atthe control valve during the dumping or lifting operation.

According to the present invention these difficulties are eliminated bymeans of a hydraulic actuator for the carburetor throttle of the truckengine that permits the engine to operate at idling speed whenever thereis no lifting load on the pump, i.e., whenever the back pressure on thepump is at a comparatively low value, and opens the throttle to apredetermined amount to give the desired speed of engine operationwhenever the hydraulic cylinder is operated to lift the body, platformor the like, i.e., whenever the back pressure on the outlet side of thepump exceeds a predetermined amount.

A general object of the present invention is the provision of a simple,substantially foolproof device for controlling the speed of operation oftruck engines so as autonited States Patent O matically to increase thespeed of the engine whenever it is desired to lift a load by thehydraulic cylinder and automatically to reduce the engine speed to theidling rate when the load is removed. Another object is the provision ofa sturdy device of this character which can be manufactured atcomparatively low cost and which can be readily installed on an existingtruck engine and in connection with conventional hydraulic systems. Afurther object is the provision of such a device which is adapted tomeet the requirements of various installations and operating conditions.Further objects and advantages of the invention will become apparentfrom the following description of a preferred form thereof, referencebeing made to the accompanying drawings. The essential characteristicsare summarized in the claims.

Referring to the drawings,

Figure 1 shows the control apparatus of the present invention as it maybe applied to a truck having a hydraulically actuated dump body;

Figure 2 is a diagram showing the hydraulic circuits of the apparatus ofFigure l; and

Figure 3 is a longitudinal sectional view on an enlarged scaleillustrating a preferred form of hydraulic device consisting of acylinder and piston mechanism for operating the engine throttle.

As shown in Figure 1 of the drawing, the control device may be adaptedto a conventional motor truck indicated in broken lines at T. Truck Thas a chassis 10, a dump body 11 and a hydraulic lifting cylinder 12embodying a piston 13 and piston rod 14. The cylinder and piston actbetween the chassis and the dump body 11 and operate so as to raise andlower the body to and from the dumping position as shown in the drawingwhen fluid under pressure is admitted to and withdrawn from cylinder 12.

Fluid under pressure is supplied to the cylinder 12 by the pump 15 whichis driven from the conventional power take off unit 17 associated withthe truck transmission 18. Thus, power for pump 15 may be furnished bythe truck engine 19. The flow of hydraulic fluid to and from thecylinder 12 is controlled by the control valve 20 which preferably ismounted outside of the truck cab at a point where the operator canobserve the motion and position of the dump body 11. Fluid returningfrom the cylinder 12 is discharged into a sump or tank 21 which isconnected to the intake side of the pump 15 to complete the hydrauliccircuit. The speed of the engine 19 is controlled by a conventionalthrottle or butterfly valve operated through lever 22 disposed adjacentthe carburetor 23. All of these elements may be of conventionalconstruction. The opening of the throttle is automatically controlled bya pressure responsive mechanism preferably comprising a hydrauliccylinder and piston assembly indicated in general at 25 in Figures 1 and2 and which will be described in detail below, this mechanism preferablybeing connected to the lever 22 through a flexible tension element suchas the non-kinking chain 26; the chain acts as a slip or lost motionconnection so that there is no interference with ordinary control of theengine throttle in driving the truck.

Referring now to Figures 2 and 3 of the drawings, the

hydraulic circuits include a pump outlet conduit 30 extending from theoutlet side of pump 15 to valve 20, a cylinder conduit 31 extending fromthe valve 20 to the lower end of the cylinder 12, a return conduit 32ex: tending from the valve 20 to the tank or sump 21, and a pump intakeconduit 33 extending from tank or sump 21 to the intake side of pump 15.The valve 20 may be of conventional construction, is operated by handle34 and is arranged so that when the valve is in the central positionshown in broken lines and indicated at a, the control is in neutral andthe liquid is simply circulated by the thid'fighth conduit 30 to thevalve 20, then thfdiigli coridnit" 32' to the sump 21 and throughconduit 33 back to the pump. With the valve in this position the onlyback, pressure on-the pump is created by pressuredfopiintheflfluid'lines,and in a properly designed systemthispressnredrepis'lo'was' compared to operating pressures;

whenfthe'handle' 3 4" is moved to the full line position 7 sh'oWn'at bthe fluid supplied to the valve through the conduitf30' is pumpedthrough conduit 31 to cylinder 12. Thus, a load is placed upon the pump15 and the pressure in' conduit 3t) promptly increases substantiallyabove the normal'idling or neutral pressure on the pump.

The valve is arranged so that pressure can be retainedwithin'the'cylinder' 12 'nierely'by moving the handle 34 back'ftoposition a at which time the fluid within the cylinder" is' lockedtherein while the fluid displaced by the unters simply re-circulated asdescribed above and the back pressure on the pump is reduced. The piston13' tween the back pressure on pump 15 under the no load' conditions-ofvalve handle positions a and c and the backi'pres's'ure on the pumpunder the load condition'of position b is utilized to control the enginethrottle so that the engine is idled' whenever the valve is in neutralposition or in position to lower the load and is operated atapredete'rminedincreased speed whenever the valve ajssaeoa r '4' inginto bore 44 and'provided with a fluid coupling 55 for connectingchamber 44 of cylinder 40 to conduit 56. Conduit 56 is connected toconduit 32 at any convenient point as shown in Figure 2, and thus thepressure in sump 21 is reflected within chamber 44 of cylinder 40. Thehigh pressure side of the fluid system is connected to cylinder 40through an opening 61 that is provided with r a fluid coupling 62 forconnecting -chamber'57 of cylinder is -'nioved to the position to raisethe load. This is accomplished by theapparatus indicated in general at25 in Figures 1 and 2 and shown in enlarged section in Figured.Referring particularly to Figure 3, the control apparatus 25 comprises acylinder 40 supported by abracket' 41 which in turn may be mounted atany con venient location within the engine-compartment, for example, onthe cylinder head of engine 19. Within cylinder'40 is a piston 42mounted on a piston rod 43. It will. be noted that piston 42- is notprovided with any fluid-tight packing or rings. 7

Piston 42 operates in bore 44 of the cylinder 40 which is threaded as at49 to receive end cap, 50 which consti tutes' the head of cylinder 40.End cap Si) is provided with a central bore 51 beginning at its insideend and extending'into, but not through, the end cap and ending atend'wall- 52; the bore 51 acts as a guide and the end wall provides astop for piston rod 43 to limit movement of the piston and rod-to theleft as shown in Figure *3. There is sufficient clearance between bore51 and the pis ton-rod to prevent trapping of fluid in the bore exceptthat the action of the piston rod in the bore preferably gives a-slightcushioning effect. Piston rod 43 is connected to chain 26, which asnoted above is connected to actuate the engine throttle. Movement of thepiston to the left in the arrangement shown in the drawings opens thethrottle; .movement' to the right permits the throttle to close.Cylinder 40 has a bore 57 of reduced diameter which is threaded as at 58at'the end remote from cylinder head 50 to receive a centrally bored nut59 which also, guides piston rod 43. Nut 59 embodies a u conventionalfluid tight packing such asQ-ring packing 60 disposedin an appropriategroove in the central bore of nut 59; At the endremote from cylinderhead 50 bore-44 terminates inan inwardly extending shoulder 53 providedby the reduced diameter bore 57.- Shoulder 53 acts as a'stop to limitthe movement of piston '42 to the, right as viewed in" Figure 3. e

40 to conduit 63, Conduit 63 is connected to conduit 30 at anyconvenientpoint arid thus the discharge=pres sure of pump 15-is reflected withinchamber-57 offcylinder 40. a

In order to return the piston 42 to the position shown in Figure 3consequentrupon a reduction of pressure within'chamber 57, a spring'64is disposed concentrically of piston rod 43 between piston 42 andcylinder head 59. When control apparatus 25 is assembled as shown inFigure 3, spring 64 is compressed-between cylinder head 50 and piston 42so that under no load conditions with the valve control handle 34 ineither of positions a or c, the spring 64 retains piston 42 in theposition: shown'in Figure 3 against the comparatively low back: pressureupon the pump 15 existing in lines 63 and 30;

However, when the valve handle 3 4-is moved to-position a and the pump15 placed under load, the increased back pressure upon the pump movesthe piston to the left in cylinder 40 against the action of the sprin'gandopens the engine throttle. As the fluid pressureinchamber 57 forcespiston 42 to the left in Figure 3, a point is reached where the pistonuncovers part of port 54 in the wall of cylinder- 40 connected toconduit 56. When the piston is in this position, therefore, the totalnet: pressure forcing the piston against the spring is reduced" ascompared to the pump discharge pressure, becausefluid is permitted tobypass the piston 42 and flow to the return conduit 56. Thus the pistonreaches a .point of substantial equilibrium where the pressure in'bore57 is substantially balanced by the'spring 64 and the tension of thechain 26, connecting the piston rod to the engine throttle. Ordinaryincreases in pump pressure move-the, piston very slightly whenthislcondition isreached be-' cause the piston uncovers more of theopening54ias it moves to the left. The result is that in normal operation the piston floats in a range in'which a small portion of theopening 54 is uncovered and unduemovement of. the piston and throttle isprevented without requiringaa verystifi spring. Thus, the throttle isopened promptly with a relatively low back pressure on. the pump, butthe presence of the return opening 54 prevents excessive opening of thethrottle and overspeeding of theengine: under all normal conditions;However, if for any reason" unusually high pressures'are developeduinbore'57', the wall 52 acts as a stop for the piston rod '43 toproviders" fixed limit to the distance the-piston canmove'to the leftand to the amount of opening of the engine throttle." Inasmuch as piston53 is not provided with any packing or: rings, there is a small amountof leakage between piston 42 and the wall of bore 44. The leakageflowing backthrough return line 56, does not substantially affect'theoperation'of the device, but the freedom of movement and small amount offriction between the piston andthe wall of bore 44 make it possible forthe spring" 64 The :cylinder'40'is connected 1nto the low pressure sideof fluid s'ystemby means of a por't-oropening 54extend-j to move thepiston back to' its original positionimmediately upon reduction of thepump pressure;

7 The movement of the piston controls the'throttle and hence the speedof the engine 19 through suitable means such as the flexible chain 26.The proper length chain is such that the chain is slightly slack whenpiston- 42. isin the position shown in Figure 3 under no load con'-'ditions so that the conventional spring in the engine throttle mechanismcan operate to move the throttle to idling position. However, whenthepressure withi'n the cylinder 40 builds up by reason of a load on thepump 15, the piston moves to the left (Figure 3) and the-pistonrod 43applies tension-to 'chain 26-, ,thereby openingithe;

throttle slightly and speeding up the engine and further building up thepressure within the system. Thus, the speed of the engine is increaseduntil further opening of the throttle is prevented either by a balanceof the net pressure on the piston and the force exerted by the spring inopposition thereto or, in some circumstances, by engagement of pistonrod 43 with the end wall 52 of central bore 51 in cylinder head 50. Byadjustment of the length of flexible chain 26 and, if desired,adjustment of the point of connection of the chain to lever 22, thespeed to which the engine is accelerated under load may be set to adesired range. In operation and with the device properly adjusted thetruck driver merely engages the power take ofi unit 17 to startoperation of the pump. Thereafter, he leaves the truck cab with thethrottle in idling position, goes to the proper station by the controlvalve 20 and operates the control valve handle 34 to raise and lower thetruck body and load as desired. Whenever the pump is under load, thetruck engine automatically accelerates to the desired speed to giveample power for lifting the load, but overspeeding of the engine isprevented by the floating action of the piston with respect to the port54. Whenever the load on the pump 15 is removed, the engine immediatelydecelerates to idling speed, thus saving fuel and wear and tear on theengine. Because of the action of the piston in uncovering port 54, thestrength of the spring is not critical so long as it has sufiicientstrength to return the piston to its initial position promptly uponreduction in pump pressure. The elimination of packing for the pistonnot only reduces manufacturing costs, but also makes the device morequickly responsive to changes in pump pressure. The device is simple andfoolproof, can be manufactured at low cost and can be adapted readily tovarious makes of trucks and different operating conditions. The devicedoes not interfere with ordinary manual control of the throttle indriving the truck.

Those skilled in the art will appreciate that various changes andmodifications can be made in the preferred form of apparatus describedherein without departing from the spirit and scope of the invention.

I claim:

1. In combination with an engine having a throttle and a pump driven bysaid engine, an automatic control device for controlling the throttle ofsaid engine, said automatic control device comprising a cylinder, meansfor fixedly supporting said cylinder relative to said engine, a pistonin said cylinder, said piston having a non-fluid tight fit in saidcylinder, a conduit connected to said cylinder on one side of saidpiston and communicating with the outlet side of said pump, wherebypressure on the outlet side of said pump tends to move said piston inone direction, a second conduit connected to said cylinder on theopposite side of said piston from the first said conduit andcommunicating with the inlet side of said pump, a piston rod secured tosaid piston and extending to the exterior of said cylinder on the sameside on Which the conduit communicating with the outlet side of saidpump is connected and extending on the other side of said piston withinthe interior of said cylinder, a spring engaging said piston andsurrounding said piston rod for moving the piston in the oppositedirection, a cylinder head on said cylinder at the opposite end fromthat through which said piston rod extends to exterior of said cylinderembodying a piston rod guide and stop to limit the movement of saidpiston rod toward said cylinder head and engaging the end of saidspring, a flexible chain for operatively connecting said piston rod tothe throttle of the engine to open the throttle upon movement of saidpiston in response to an increase in fluid pressure in said cylinder,and to permit the throttle to close upon movement of said piston in theopposite direction under the influence of said spring when the fluidpressure in the cylinder is reduced.

2. In combination with, an engine having a throttle and a pump driven bysaid engine, an automatic control device for controlling the throttle ofsaid engine, said automatic control device comprising a cylinder, meansfor fixedly supporting said cylinder relative to said engine, a pistonin said cylinder, said piston having a non-fluid tight fit in saidcylinder, a conduit connected to said cylinder on one side of saidpiston and communicating with the outlet side of said pump, wherebypressure on the outlet side of said pump tends to move said piston inone direction, a second conduit connected to said cylinder on theopposite side of said piston from the first said conduit andcommunicating with the inlet side of said pump, whereby the pressure onthe inlet side of said pump tends to exhaust the cylinder on that sideof the piston to which said second conduit connects, a piston rodsecured to said piston and extending to the exterior of said cylinder onthe same side on which the conduit communicating with the outlet side ofsaid pump is connected and extending on the other side of said pistonwithin the interior of said cylinder, a spring engaging said piston andsurrounding said piston rod for moving the piston in the oppositedirection, an internal shoulder within said cylinder engageable withsaid piston for limiting the movement of said piston in response topressure in said cylinder, a cylinder head on said cylinder at theopposite end from that through which said piston rod extends to exteriorof said cylinder embodying a piston rod guide and engaging the end ofsaid spring, a flexible chain for operatively connecting said piston rodto the throttle of the engine to open the throttle upon movement of saidpiston in response to an increase in fluid pressure in sald cylinder,and to permit the throttle to close upon movement of said piston in theopposite direction under the influence of said spring when the fluidpressure in the cylinder is reduced.

3. In combination with an engine having a throttle and a pump driven bysaid engine, an automatic control device for controlling the throttle ofsaid engine, said automatic control device comprising a cylinder, ameans for supporting said cylinder relative to said engine, a piston insaid cylinder, said piston having a non-fluid tight fit in saidcylinder, a conduit connected to said cylinder on one side of saidpiston and communicating with the outlet side of said pump whereby thedischarge pressure of the pump tends to move said piston in onedirection, said cylinder having a port and a second conduit connected tosaid port on the opposite side of said piston from the first saidconduit and communicating with the inlet side of said pump, said portbeing in a positlon to be uncovered by said piston after a predeterminedmovement of said piston in response to pressure in said cylinder, apiston rod secured to said piston and extending to the exterior of saidcylinder, a spring engaging said piston and tending to move said pistonin the opposite direction and a lost motion connection for operativelyconnecting said piston rod to the throttle of the engine to open thethrottle upon movement of said piston in said one direction in responseto an increase in fluid pressure in said cylinder, and to permit thethrottle to close upon movement of said piston in the opposite directionunder the influence of said spring when the fluid pressure in thecylinder is reduced.

References Cited in the file of this patent UNITED STATES PATENTS825,718 Grimes July 10, 1906 1,259,090 Ferris et al. Mar. 12, 19182,234,798 Craig Mar. 11, 1941 2,292,294 Rotter Aug. 4, 1942 2,364,812Pierson Dec. 12, 1944 2,642,805 Nepper June 23, 1953 2,690,712 FooteOct. 5, 1954 2,800,921 Wright July 30, 1957

